On Mon, Apr 29, 2024 at 04:46:00PM -0600, Daniel Xu wrote:
> This commit teaches pahole to parse symbols in .BTF_ids section in
> vmlinux and discover exported kfuncs. Pahole then takes the list of
> kfuncs and injects a BTF_KIND_DECL_TAG for each kfunc.
>
> Example of encoding:
>
> $ bpftool btf dump file .tmp_vmlinux.btf | rg "DECL_TAG 'bpf_kfunc'" | wc -l
> 121
>
> $ bpftool btf dump file .tmp_vmlinux.btf | rg 56337
> [56337] FUNC 'bpf_ct_change_timeout' type_id=56336 linkage=static
> [127861] DECL_TAG 'bpf_kfunc' type_id=56337 component_idx=-1
>
> This enables downstream users and tools to dynamically discover which
> kfuncs are available on a system by parsing vmlinux or module BTF, both
> available in /sys/kernel/btf.
>
> This feature is enabled with --btf_features=decl_tag,decl_tag_kfuncs.
I'm trying this but:
⬢[acme@toolbox pahole]$ time pahole -j --btf_features=decl_tag,decl_tag_kfuncs --btf_encode_detached=vmlinux.btf.decl_tag,decl_tag_kfuncs vmlinux
btf_encoder__tag_kfuncs(cgroup_rstat_updated): found=0
btf_encoder__tag_kfuncs(cgroup_rstat_flush): found=0
btf_encoder__tag_kfuncs(security_file_permission): found=0
btf_encoder__tag_kfuncs(security_inode_getattr): found=0
btf_encoder__tag_kfuncs(security_file_open): found=0
btf_encoder__tag_kfuncs(security_path_truncate): found=0
btf_encoder__tag_kfuncs(vfs_truncate): found=0
btf_encoder__tag_kfuncs(vfs_fallocate): found=0
btf_encoder__tag_kfuncs(dentry_open): found=0
btf_encoder__tag_kfuncs(vfs_getattr): found=0
btf_encoder__tag_kfuncs(filp_close): found=0
btf_encoder__tag_kfuncs(bpf_lookup_user_key): found=0
btf_encoder__tag_kfuncs(bpf_lookup_system_key): found=0
btf_encoder__tag_kfuncs(bpf_key_put): found=0
btf_encoder__tag_kfuncs(bpf_verify_pkcs7_signature): found=0
btf_encoder__tag_kfuncs(bpf_obj_new_impl): found=0
<SNIP all with found=0>
With:
⬢[acme@toolbox pahole]$ git diff -U16
diff --git a/btf_encoder.c b/btf_encoder.c
index c2df2bc7a374447b..27a16d6564381b60 100644
--- a/btf_encoder.c
+++ b/btf_encoder.c
@@ -1689,32 +1689,35 @@ static int btf_encoder__tag_kfuncs(struct btf_encoder *encoder)
func = get_func_name(name);
if (!func)
continue;
/* Check if function belongs to a kfunc set */
ranges = gobuffer__entries(&btf_kfunc_ranges);
ranges_cnt = gobuffer__nr_entries(&btf_kfunc_ranges);
found = false;
for (j = 0; j < ranges_cnt; j++) {
size_t addr = sym.st_value;
if (ranges[j].start <= addr && addr < ranges[j].end) {
found = true;
break;
}
}
+
+ printf("%s(%s): found=%d\n", __func__, func, found);
+
if (!found) {
free(func);
continue;
}
err = btf_encoder__tag_kfunc(encoder, &btf_funcs, func);
if (err) {
fprintf(stderr, "%s: failed to tag kfunc '%s'\n", __func__, func);
free(func);
goto out;
}
free(func);
}
err = 0;
out:
--------------
The vmlinux I'm testing on has the kfuncs, etc, as we can see with:
⬢[acme@toolbox pahole]$ readelf -sW vmlinux | grep __BTF_ID__func__ | wc -l
517
⬢[acme@toolbox pahole]$ readelf -sW vmlinux | grep __BTF_ID__func__ | tail
97887: ffffffff83266bfc 4 OBJECT LOCAL DEFAULT 15 __BTF_ID__func__cubictcp_cong_avoid__805493
97888: ffffffff83266c04 4 OBJECT LOCAL DEFAULT 15 __BTF_ID__func__cubictcp_state__806494
97889: ffffffff83266c0c 4 OBJECT LOCAL DEFAULT 15 __BTF_ID__func__cubictcp_cwnd_event__807495
97890: ffffffff83266c14 4 OBJECT LOCAL DEFAULT 15 __BTF_ID__func__cubictcp_acked__808496
98068: ffffffff83266c24 4 OBJECT LOCAL DEFAULT 15 __BTF_ID__func__tcp_reno_ssthresh__773199
98069: ffffffff83266c2c 4 OBJECT LOCAL DEFAULT 15 __BTF_ID__func__tcp_reno_cong_avoid__774200
98070: ffffffff83266c34 4 OBJECT LOCAL DEFAULT 15 __BTF_ID__func__tcp_reno_undo_cwnd__775201
98071: ffffffff83266c3c 4 OBJECT LOCAL DEFAULT 15 __BTF_ID__func__tcp_slow_start__776202
98072: ffffffff83266c44 4 OBJECT LOCAL DEFAULT 15 __BTF_ID__func__tcp_cong_avoid_ai__777203
101522: ffffffff83266c5c 4 OBJECT LOCAL DEFAULT 15 __BTF_ID__func__update_socket_protocol__80024
⬢[acme@toolbox pahole]$
So that btf_encoder__tag_kfuncs() isn't finding any?
$ pahole -j --btf_features=decl_tag,decl_tag_kfuncs --btf_encode_detached=vmlinux.btf.decl_tag,decl_tag_kfuncs vmlinux
btf_encoder__tag_kfuncs(vmlinux)
Yeah, getting the source filename, the right one.
Then is_sym_kfunc_set() never returns true... But:
⬢[acme@toolbox pahole]$ time pahole -j --btf_features=decl_tag,decl_tag_kfuncs --btf_encode_detached=vmlinux.btf.decl_tag,decl_tag_kfuncs vmlinux
is_sym_kfunc_set(__BTF_ID__set8__bpf_rstat_kfunc_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__)
is_sym_kfunc_set(__BTF_ID__set8__key_sig_kfunc_set, BTF_ID_SET8_PFX=__BTF_ID__set8__)
is_sym_kfunc_set(__BTF_ID__set8__generic_btf_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__)
is_sym_kfunc_set(__BTF_ID__set8__common_btf_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__)
is_sym_kfunc_set(__BTF_ID__set8__bpf_map_iter_kfunc_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__)
is_sym_kfunc_set(__BTF_ID__set8__cpumask_kfunc_btf_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__)
is_sym_kfunc_set(__BTF_ID__set8__hid_bpf_kfunc_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__)
is_sym_kfunc_set(__BTF_ID__set8__hid_bpf_fmodret_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__)
is_sym_kfunc_set(__BTF_ID__set8__hid_bpf_syscall_kfunc_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__)
is_sym_kfunc_set(__BTF_ID__set8__bpf_kfunc_check_set_skb, BTF_ID_SET8_PFX=__BTF_ID__set8__)
is_sym_kfunc_set(__BTF_ID__set8__bpf_kfunc_check_set_xdp, BTF_ID_SET8_PFX=__BTF_ID__set8__)
is_sym_kfunc_set(__BTF_ID__set8__bpf_kfunc_check_set_sock_addr, BTF_ID_SET8_PFX=__BTF_ID__set8__)
is_sym_kfunc_set(__BTF_ID__set8__bpf_sk_iter_kfunc_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__)
is_sym_kfunc_set(__BTF_ID__set8__xdp_metadata_kfunc_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__)
is_sym_kfunc_set(__BTF_ID__set8__bpf_test_modify_return_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__)
is_sym_kfunc_set(__BTF_ID__set8__test_sk_check_kfunc_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__)
is_sym_kfunc_set(__BTF_ID__set8__tcp_cubic_check_kfunc_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__)
is_sym_kfunc_set(__BTF_ID__set8__bpf_tcp_ca_check_kfunc_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__)
is_sym_kfunc_set(__BTF_ID__set8__bpf_mptcp_fmodret_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__)
real 0m5.586s
user 0m29.707s
sys 0m2.160s
⬢[acme@toolbox pahole]$
And then:
⬢[acme@toolbox pahole]$ time pahole -j --btf_features=decl_tag,decl_tag_kfuncs --btf_encode_detached=vmlinux.btf.decl_tag,decl_tag_kfuncs vmlinux
is_sym_kfunc_set(__BTF_ID__set8__bpf_rstat_kfunc_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__, set->flags= 0, BTF_SET8_KFUNCS=1, ret=0)
is_sym_kfunc_set(__BTF_ID__set8__key_sig_kfunc_set, BTF_ID_SET8_PFX=__BTF_ID__set8__, set->flags= 0, BTF_SET8_KFUNCS=1, ret=0)
is_sym_kfunc_set(__BTF_ID__set8__generic_btf_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__, set->flags= 0, BTF_SET8_KFUNCS=1, ret=0)
is_sym_kfunc_set(__BTF_ID__set8__common_btf_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__, set->flags= 0, BTF_SET8_KFUNCS=1, ret=0)
is_sym_kfunc_set(__BTF_ID__set8__bpf_map_iter_kfunc_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__, set->flags= 0, BTF_SET8_KFUNCS=1, ret=0)
is_sym_kfunc_set(__BTF_ID__set8__cpumask_kfunc_btf_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__, set->flags= 0, BTF_SET8_KFUNCS=1, ret=0)
is_sym_kfunc_set(__BTF_ID__set8__hid_bpf_kfunc_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__, set->flags= 0, BTF_SET8_KFUNCS=1, ret=0)
is_sym_kfunc_set(__BTF_ID__set8__hid_bpf_fmodret_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__, set->flags= 0, BTF_SET8_KFUNCS=1, ret=0)
is_sym_kfunc_set(__BTF_ID__set8__hid_bpf_syscall_kfunc_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__, set->flags= 0, BTF_SET8_KFUNCS=1, ret=0)
is_sym_kfunc_set(__BTF_ID__set8__bpf_kfunc_check_set_skb, BTF_ID_SET8_PFX=__BTF_ID__set8__, set->flags= 0, BTF_SET8_KFUNCS=1, ret=0)
is_sym_kfunc_set(__BTF_ID__set8__bpf_kfunc_check_set_xdp, BTF_ID_SET8_PFX=__BTF_ID__set8__, set->flags= 0, BTF_SET8_KFUNCS=1, ret=0)
is_sym_kfunc_set(__BTF_ID__set8__bpf_kfunc_check_set_sock_addr, BTF_ID_SET8_PFX=__BTF_ID__set8__, set->flags= 0, BTF_SET8_KFUNCS=1, ret=0)
is_sym_kfunc_set(__BTF_ID__set8__bpf_sk_iter_kfunc_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__, set->flags= 0, BTF_SET8_KFUNCS=1, ret=0)
is_sym_kfunc_set(__BTF_ID__set8__xdp_metadata_kfunc_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__, set->flags= 0, BTF_SET8_KFUNCS=1, ret=0)
is_sym_kfunc_set(__BTF_ID__set8__bpf_test_modify_return_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__, set->flags= 0, BTF_SET8_KFUNCS=1, ret=0)
is_sym_kfunc_set(__BTF_ID__set8__test_sk_check_kfunc_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__, set->flags= 0, BTF_SET8_KFUNCS=1, ret=0)
is_sym_kfunc_set(__BTF_ID__set8__tcp_cubic_check_kfunc_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__, set->flags= 0, BTF_SET8_KFUNCS=1, ret=0)
is_sym_kfunc_set(__BTF_ID__set8__bpf_tcp_ca_check_kfunc_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__, set->flags= 0, BTF_SET8_KFUNCS=1, ret=0)
is_sym_kfunc_set(__BTF_ID__set8__bpf_mptcp_fmodret_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__, set->flags= 0, BTF_SET8_KFUNCS=1, ret=0)
real 0m5.597s
user 0m29.620s
sys 0m2.138s
⬢[acme@toolbox pahole]$
Run out of time, I probably am using an old vmlinux, will try later with
one generated from a current kernel, or maybe you guys point to my
st00pidity saying what I am missing 8-)
- Arnaldo
